Move the kvm_cpu_{un}init() calls to common PPC code as an intermediate
step towards removing kvm_cpu_{un}init() altogether.
No functional change intended.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Move the initialization of oldpir so that the call to kvm_vcpu_init() is
at the top of kvmppc_core_vcpu_create_e500mc(). oldpir is only use
when loading/putting a vCPU, which currently cannot be done until after
kvm_arch_vcpu_create() completes. Reording the call to kvm_vcpu_init()
paves the way for moving the invocation to common PPC code.
No functional change intended.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Call kvm_vcpu_init() in kvmppc_core_vcpu_create_pr() prior to allocating
the book3s and shadow_vcpu objects in preparation of moving said call to
common PPC code. Although kvm_vcpu_init() has an arch callback, the
callback is empty for Book3S PR, i.e. barring unseen black magic, moving
the allocation has no real functional impact.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Move allocation of all flavors of PPC vCPUs to common PPC code. All
variants either allocate 'struct kvm_vcpu' directly, or require that
the embedded 'struct kvm_vcpu' member be located at offset 0, i.e.
guarantee that the allocation can be directly interpreted as a 'struct
kvm_vcpu' object.
Remove the message from the build-time assertion regarding placement of
the struct, as compatibility with the arch usercopy region is no longer
the sole dependent on 'struct kvm_vcpu' being at offset zero.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
In preparation for moving vcpu allocation to common PPC code, add an
explicit, albeit redundant, build-time assert to ensure the vcpu member
is located at offset 0. The assert is redundant in the sense that
kvmppc_core_vcpu_create_e500() contains a functionally identical assert.
The motiviation for adding the extra assert is to provide visual
confirmation of the correctness of moving vcpu allocation to common
code.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Move the kvm_cpu_{un}init() calls to common x86 code as an intermediate
step to removing kvm_cpu_{un}init() altogether.
Note, VMX'x alloc_apic_access_page() and init_rmode_identity_map() are
per-VM allocations and are intentionally kept if vCPU creation fails.
They are freed by kvm_arch_destroy_vm().
No functional change intended.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Allocate the pio_data page after creating the MMU and local APIC so that
all direct memory allocations are grouped together. This allows setting
the return value to -ENOMEM prior to starting the allocations instead of
setting it in the fail path for every allocation.
The pio_data page is only consumed when KVM_RUN is invoked, i.e. moving
its allocation has no real functional impact.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The allocation of FPU structs is identical across VMX and SVM, move it
to common x86 code. Somewhat arbitrarily place the allocation so that
it resides directly above the associated initialization via fx_init(),
e.g. instead of retaining its position with respect to the overall vcpu
creation flow. Although the names names kvm_arch_vcpu_create() and
kvm_arch_vcpu_init() might suggest otherwise, x86 does not have a clean
split between 'create' and 'init'. Allocating the struct immediately
prior to the first use arguably improves readability *now*, and will
yield even bigger improvements when kvm_arch_vcpu_init() is removed in
a future patch.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Move allocation of VMX and SVM vcpus to common x86. Although the struct
being allocated is technically a VMX/SVM struct, it can be interpreted
directly as a 'struct kvm_vcpu' because of the pre-existing requirement
that 'struct kvm_vcpu' be located at offset zero of the arch/vendor vcpu
struct.
Remove the message from the build-time assertions regarding placement of
the struct, as compatibility with the arch usercopy region is no longer
the sole dependent on 'struct kvm_vcpu' being at offset zero.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Capture the vcpu pointer in a local varaible and replace '&svm->vcpu'
references with a direct reference to the pointer in anticipation of
moving bits of the code to common x86 and passing the vcpu pointer into
svm_create_vcpu(), i.e. eliminate unnecessary noise from future patches.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Capture the vcpu pointer in a local varaible and replace '&vmx->vcpu'
references with a direct reference to the pointer in anticipation of
moving bits of the code to common x86 and passing the vcpu pointer into
vmx_create_vcpu(), i.e. eliminate unnecessary noise from future patches.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Do VPID allocation after calling the common kvm_vcpu_init() as a step
towards doing vCPU allocation (via kmem_cache_zalloc()) and calling
kvm_vcpu_init() back-to-back. Squishing allocation and initialization
together will eventually allow the sequence to be moved to arch-agnostic
creation code.
Note, the VPID is not consumed until KVM_RUN, slightly delaying its
allocation should have no real function impact. VPID allocation was
arbitrarily placed in the original patch, commit 2384d2b326 ("KVM:
VMX: Enable Virtual Processor Identification (VPID)").
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Free the vCPU's wbinvd_dirty_mask if vCPU creation fails after
kvm_arch_vcpu_init(), e.g. when installing the vCPU's file descriptor.
Do the freeing by calling kvm_arch_vcpu_free() instead of open coding
the freeing. This adds a likely superfluous, but ultimately harmless,
call to kvmclock_reset(), which only clears vcpu->arch.pv_time_enabled.
Using kvm_arch_vcpu_free() allows for additional cleanup in the future.
Fixes: f5f48ee15c ("KVM: VMX: Execute WBINVD to keep data consistency with assigned devices")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Explicitly free the shared page if kvmppc_mmu_init() fails during
kvmppc_core_vcpu_create(), as the page is freed only in
kvmppc_core_vcpu_free(), which is not reached via kvm_vcpu_uninit().
Fixes: 96bc451a15 ("KVM: PPC: Introduce shared page")
Cc: stable@vger.kernel.org
Reviewed-by: Greg Kurz <groug@kaod.org>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Acked-by: Paul Mackerras <paulus@ozlabs.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Call kvm_vcpu_uninit() if vcore creation fails to avoid leaking any
resources allocated by kvm_vcpu_init(), i.e. the vcpu->run page.
Fixes: 371fefd6f2 ("KVM: PPC: Allow book3s_hv guests to use SMT processor modes")
Cc: stable@vger.kernel.org
Reviewed-by: Greg Kurz <groug@kaod.org>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Acked-by: Paul Mackerras <paulus@ozlabs.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
If the guest is configured to have SPEC_CTRL but the host does not
(which is a nonsensical configuration but these are not explicitly
forbidden) then a host-initiated MSR write can write vmx->spec_ctrl
(respectively svm->spec_ctrl) and trigger a #GP when KVM tries to
restore the host value of the MSR. Add a more comprehensive check
for valid bits of SPEC_CTRL, covering host CPUID flags and,
since we are at it and it is more correct that way, guest CPUID
flags too.
For AMD, remove the unnecessary is_guest_mode check around setting
the MSR interception bitmap, so that the code looks the same as
for Intel.
Cc: Jim Mattson <jmattson@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The wrappers make it less clear that the position of the call
to kvm_arch_async_page_present depends on the architecture, and
that only one of the two call sites will actually be active.
Remove them.
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Even if it's read-only, it can still be written to by userspace. Let
them know by adding it to KVM_GET_MSR_INDEX_LIST.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The filter name is fixed to "exit_reason" for some kvm_exit events, no
matter what architect we have. Actually, the filter name ("exit_reason")
is only applicable to x86, meaning it's broken on other architects
including aarch64.
This fixes the issue by providing various kvm_exit filter names, depending
on architect we're on. Afterwards, the variable filter name is picked and
applied through ioctl(fd, SET_FILTER).
Reported-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Gavin Shan <gshan@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The SPTE_MMIO_MASK overlaps with the bits used to track MMIO
generation number. A high enough generation number would overwrite the
SPTE_SPECIAL_MASK region and cause the MMIO SPTE to be misinterpreted.
Likewise, setting bits 52 and 53 would also cause an incorrect generation
number to be read from the PTE, though this was partially mitigated by the
(useless if it weren't for the bug) removal of SPTE_SPECIAL_MASK from
the spte in get_mmio_spte_generation. Drop that removal, and replace
it with a compile-time assertion.
Fixes: 6eeb4ef049 ("KVM: x86: assign two bits to track SPTE kinds")
Reported-by: Ben Gardon <bgardon@google.com>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
We can store reference to kvm_stats_debugfs_item instead of copying
its values to kvm_stat_data.
This allows us to remove duplicated code and usage of temporary
kvm_stat_data inside vm_stat_get et al.
Signed-off-by: Milan Pandurov <milanpa@amazon.de>
Reviewed-by: Alexander Graf <graf@amazon.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Remove the bogus 64-bit only condition from the check that disables MMIO
spte optimization when the system supports the max PA, i.e. doesn't have
any reserved PA bits. 32-bit KVM always uses PAE paging for the shadow
MMU, and per Intel's SDM:
PAE paging translates 32-bit linear addresses to 52-bit physical
addresses.
The kernel's restrictions on max physical addresses are limits on how
much memory the kernel can reasonably use, not what physical addresses
are supported by hardware.
Fixes: ce88decffd ("KVM: MMU: mmio page fault support")
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
In case writing to vmread destination operand result in a #PF, vmread
should not call nested_vmx_succeed() to set rflags to specify success.
Similar to as done in VMPTRST (See handle_vmptrst()).
Reviewed-by: Liran Alon <liran.alon@oracle.com>
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Cc: stable@vger.kernel.org
Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Rework the handling of nEPT's bad memtype/XWR checks to micro-optimize
the checks as much as possible. Move the check to a separate helper,
__is_bad_mt_xwr(), which allows the guest_rsvd_check usage in
paging_tmpl.h to omit the check entirely for paging32/64 (bad_mt_xwr is
always zero for non-nEPT) while retaining the bitwise-OR of the current
code for the shadow_zero_check in walk_shadow_page_get_mmio_spte().
Add a comment for the bitwise-OR usage in the mmio spte walk to avoid
future attempts to "fix" the code, which is what prompted this
optimization in the first place[*].
Opportunistically remove the superfluous '!= 0' and parantheses, and
use BIT_ULL() instead of open coding its equivalent.
The net effect is that code generation is largely unchanged for
walk_shadow_page_get_mmio_spte(), marginally better for
ept_prefetch_invalid_gpte(), and significantly improved for
paging32/64_prefetch_invalid_gpte().
Note, walk_shadow_page_get_mmio_spte() can't use a templated version of
the memtype/XRW as it works on the host's shadow PTEs, e.g. checks that
KVM hasn't borked its EPT tables. Even if it could be templated, the
benefits of having a single implementation far outweight the few uops
that would be saved for NPT or non-TDP paging, e.g. most compilers
inline it all the way to up kvm_mmu_page_fault().
[*] https://lkml.kernel.org/r/20200108001859.25254-1-sean.j.christopherson@intel.com
Cc: Jim Mattson <jmattson@google.com>
Cc: David Laight <David.Laight@ACULAB.COM>
Cc: Arvind Sankar <nivedita@alum.mit.edu>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The KVM MMIO support uses bit 51 as the reserved bit to cause nested page
faults when a guest performs MMIO. The AMD memory encryption support uses
a CPUID function to define the encryption bit position. Given this, it is
possible that these bits can conflict.
Use svm_hardware_setup() to override the MMIO mask if memory encryption
support is enabled. Various checks are performed to ensure that the mask
is properly defined and rsvd_bits() is used to generate the new mask (as
was done prior to the change that necessitated this patch).
Fixes: 28a1f3ac1d ("kvm: x86: Set highest physical address bits in non-present/reserved SPTEs")
Suggested-by: Sean Christopherson <sean.j.christopherson@intel.com>
Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
The function nested_vmx_prepare_msr_bitmap() declaration is below its
implementation. So this is meaningless and should be removed.
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Reviewed-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Rename bit() to __feature_bit() to give it a more descriptive name, and
add a macro, feature_bit(), to stuff the X68_FEATURE_ prefix to keep
line lengths manageable for code that hardcodes the bit to be retrieved.
No functional change intended.
Cc: Jim Mattson <jmattson@google.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add build-time checks to ensure KVM isn't trying to do a reverse CPUID
lookup on Linux-defined feature bits, along with comments to explain
the gory details of X86_FEATUREs and bit().
No functional change intended.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add an entry for CPUID_7_1_EAX in the reserve_cpuid array in preparation
for incorporating the array in bit() build-time assertions, specifically
to avoid an assertion on F(AVX512_BF16) in do_cpuid_7_mask().
No functional change intended.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Move bit() to cpuid.h in preparation for incorporating the reverse_cpuid
array in bit() build-time assertions. Opportunistically use the BIT()
macro instead of open-coding the shift.
No functional change intended.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add feature-specific helpers for querying guest CPUID support from the
emulator instead of having the emulator do a full CPUID and perform its
own bit tests. The primary motivation is to eliminate the emulator's
usage of bit() so that future patches can add more extensive build-time
assertions on the usage of bit() without having to expose yet more code
to the emulator.
Note, providing a generic guest_cpuid_has() to the emulator doesn't work
due to the existing built-time assertions in guest_cpuid_has(), which
require the feature being checked to be a compile-time constant.
No functional change intended.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add a helper macro to generate the set of reserved cr4 bits for both
host and guest to ensure that adding a check on guest capabilities is
also added for host capabilities, and vice versa.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Now that KVM prevents setting host-reserved CR4 bits, drop the dedicated
XSAVE check in guest_cpuid_has() in favor of open coding similar checks
in the SVM/VMX XSAVES enabling flows.
Note, checking boot_cpu_has(X86_FEATURE_XSAVE) in the XSAVES flows is
technically redundant with respect to the CR4 reserved bit checks, e.g.
XSAVES #UDs if CR4.OSXSAVE=0 and arch.xsaves_enabled is consumed if and
only if CR4.OXSAVE=1 in guest. Keep (add?) the explicit boot_cpu_has()
checks to help document KVM's usage of arch.xsaves_enabled.
No functional change intended.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Check the current CPU's reserved cr4 bits against the mask calculated
for the boot CPU to ensure consistent behavior across all CPUs.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Calculate the host-reserved cr4 bits at runtime based on the system's
capabilities (using logic similar to __do_cpuid_func()), and use the
dynamically generated mask for the reserved bit check in kvm_set_cr4()
instead using of the static CR4_RESERVED_BITS define. This prevents
userspace from "enabling" features in cr4 that are not supported by the
system, e.g. by ignoring KVM_GET_SUPPORTED_CPUID and specifying a bogus
CPUID for the vCPU.
Allowing userspace to set unsupported bits in cr4 can lead to a variety
of undesirable behavior, e.g. failed VM-Enter, and in general increases
KVM's attack surface. A crafty userspace can even abuse CR4.LA57 to
induce an unchecked #GP on a WRMSR.
On a platform without LA57 support:
KVM_SET_CPUID2 // CPUID_7_0_ECX.LA57 = 1
KVM_SET_SREGS // CR4.LA57 = 1
KVM_SET_MSRS // KERNEL_GS_BASE = 0x0004000000000000
KVM_RUN
leads to a #GP when writing KERNEL_GS_BASE into hardware:
unchecked MSR access error: WRMSR to 0xc0000102 (tried to write 0x0004000000000000)
at rIP: 0xffffffffa00f239a (vmx_prepare_switch_to_guest+0x10a/0x1d0 [kvm_intel])
Call Trace:
kvm_arch_vcpu_ioctl_run+0x671/0x1c70 [kvm]
kvm_vcpu_ioctl+0x36b/0x5d0 [kvm]
do_vfs_ioctl+0xa1/0x620
ksys_ioctl+0x66/0x70
__x64_sys_ioctl+0x16/0x20
do_syscall_64+0x4c/0x170
entry_SYSCALL_64_after_hwframe+0x44/0xa9
RIP: 0033:0x7fc08133bf47
Note, the above sequence fails VM-Enter due to invalid guest state.
Userspace can allow VM-Enter to succeed (after the WRMSR #GP) by adding
a KVM_SET_SREGS w/ CR4.LA57=0 after KVM_SET_MSRS, in which case KVM will
technically leak the host's KERNEL_GS_BASE into the guest. But, as
KERNEL_GS_BASE is a userspace-defined value/address, the leak is largely
benign as a malicious userspace would simply be exposing its own data to
the guest, and attacking a benevolent userspace would require multiple
bugs in the userspace VMM.
Cc: stable@vger.kernel.org
Cc: Jun Nakajima <jun.nakajima@intel.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add a helper to consolidate the common checks for writing PT MSRs,
and opportunistically clean up the formatting of the affected code.
No functional change intended.
Cc: Chao Peng <chao.p.peng@linux.intel.com>
Cc: Luwei Kang <luwei.kang@intel.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reject writes to RTIT address MSRs if the data being written is a
non-canonical address as the MSRs are subject to canonical checks, e.g.
KVM will trigger an unchecked #GP when loading the values to hardware
during pt_guest_enter().
Cc: stable@vger.kernel.org
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Fix some typos in vcpu unimpl info. It should be unhandled rather than
uhandled.
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Fix some typos and add missing parentheses in the comments.
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Since commit b1346ab2af ("KVM: nVMX: Rename prepare_vmcs02_*_full to
prepare_vmcs02_*_rare"), prepare_vmcs02_full has been renamed to
prepare_vmcs02_rare.
nested_vmx_merge_msr_bitmap is renamed to nested_vmx_prepare_msr_bitmap
since commit c992384bde ("KVM: vmx: speed up MSR bitmap merge").
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Fix some wrong function names in comment. mmu_check_roots is a typo for
mmu_check_root, vmcs_read_any should be vmcs12_read_any and so on.
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
check kvm_pit outside kvm_vm_ioctl_reinject() to keep codestyle consistent
with other kvm_pit func and prepare for futher cleanups.
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This patch optimizes redundancy logic before fixed mode ipi is delivered
in the fast path, broadcast handling needs to go slow path, so the delivery
mode repair can be delayed to before slow path.
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
ICR and TSCDEADLINE MSRs write cause the main MSRs write vmexits in our
product observation, multicast IPIs are not as common as unicast IPI like
RESCHEDULE_VECTOR and CALL_FUNCTION_SINGLE_VECTOR etc.
This patch introduce a mechanism to handle certain performance-critical
WRMSRs in a very early stage of KVM VMExit handler.
This mechanism is specifically used for accelerating writes to x2APIC ICR
that attempt to send a virtual IPI with physical destination-mode, fixed
delivery-mode and single target. Which was found as one of the main causes
of VMExits for Linux workloads.
The reason this mechanism significantly reduce the latency of such virtual
IPIs is by sending the physical IPI to the target vCPU in a very early stage
of KVM VMExit handler, before host interrupts are enabled and before expensive
operations such as reacquiring KVM’s SRCU lock.
Latency is reduced even more when KVM is able to use APICv posted-interrupt
mechanism (which allows to deliver the virtual IPI directly to target vCPU
without the need to kick it to host).
Testing on Xeon Skylake server:
The virtual IPI latency from sender send to receiver receive reduces
more than 200+ cpu cycles.
Reviewed-by: Liran Alon <liran.alon@oracle.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Liran Alon <liran.alon@oracle.com>
Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
WARN if root_hpa is invalid when handling a page fault. The check on
root_hpa exists for historical reasons that no longer apply to the
current KVM code base.
Remove an equivalent debug-only warning in direct_page_fault(), whose
existence more or less confirms that root_hpa should always be valid
when handling a page fault.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
WARN on the existing invalid root_hpa checks in __direct_map() and
FNAME(fetch). The "legitimate" path that invalidated root_hpa in the
middle of a page fault is long since gone, i.e. it should no longer be
impossible to invalidate in the middle of a page fault[*].
The root_hpa checks were added by two related commits
989c6b34f6 ("KVM: MMU: handle invalid root_hpa at __direct_map")
37f6a4e237 ("KVM: x86: handle invalid root_hpa everywhere")
to fix a bug where nested_vmx_vmexit() could be called *in the middle*
of a page fault. At the time, vmx_interrupt_allowed(), which was and
still is used by kvm_can_do_async_pf() via ->interrupt_allowed(),
directly invoked nested_vmx_vmexit() to switch from L2 to L1 to emulate
a VM-Exit on a pending interrupt. Emulating the nested VM-Exit resulted
in root_hpa being invalidated by kvm_mmu_reset_context() without
explicitly terminating the page fault.
Now that root_hpa is checked for validity by kvm_mmu_page_fault(), WARN
on an invalid root_hpa to detect any flows that reset the MMU while
handling a page fault. The broken vmx_interrupt_allowed() behavior has
long since been fixed and resetting the MMU during a page fault should
not be considered legal behavior.
[*] It's actually technically possible in FNAME(page_fault)() because it
calls inject_page_fault() when the guest translation is invalid, but
in that case the page fault handling is immediately terminated.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Add a check on root_hpa at the beginning of the page fault handler to
consolidate several checks on root_hpa that are scattered throughout the
page fault code. This is a preparatory step towards eventually removing
such checks altogether, or at the very least WARNing if an invalid root
is encountered. Remove only the checks that can be easily audited to
confirm that root_hpa cannot be invalidated between their current
location and the new check in kvm_mmu_page_fault(), and aren't currently
protected by mmu_lock, i.e. keep the checks in __direct_map() and
FNAME(fetch) for the time being.
The root_hpa checks that are consolidate were all added by commit
37f6a4e237 ("KVM: x86: handle invalid root_hpa everywhere")
which was a follow up to a bug fix for __direct_map(), commit
989c6b34f6 ("KVM: MMU: handle invalid root_hpa at __direct_map")
At the time, nested VMX had, in hindsight, crazy handling of nested
interrupts and would trigger a nested VM-Exit in ->interrupt_allowed(),
and thus unexpectedly reset the MMU in flows such as can_do_async_pf().
Now that the wonky nested VM-Exit behavior is gone, the root_hpa checks
are bogus and confusing, e.g. it's not at all obvious what they actually
protect against, and at first glance they appear to be broken since many
of them run without holding mmu_lock.
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
